In many instances medical tubes are inserted into a patient's body for short-term or long-term infusion of medicine, blood products, nutrition or other fluids. Such tubes are inserted, for example, into the patient's venous, arterial or digestive system. Sometimes it is important to insert the medicine or other fluid into a particular point in the patient's body. For example, in cancer chemotherapy and antibiotic therapy, an outlet of the tube infusing the medicine must be positioned in an area of high volume blood flow. As another example, patients who cannot eat on their own have a feeding tube inserted through their nose or mouth into their stomach. A feeding solution is inserted into the patient's stomach through an end of the feeding tube outside of the patient's body. The feeding solution naturally must be inserted into the stomach and not into other areas of the body. Other intrabody tubes include dilating tubes to widen esophageal stricture, colonic decompression tubes and urological tubes.
In many cases, an intrabody tube is used periodically over a long period of time. Therefore, to avoid the need to repeatedly insert new tubes, the tube is left within the patient's body. This is especially important when the patient is in home care, where there is nobody who can insert the tube. Home care of patients is a widespread and growing field, mainly due to the rising cost of hospital fees and the lengthening of care periods.
Generally, there is no simple method of keeping an intrabody tube fixed in place, and the tubes do not always remain in their original place. The outlet of the tube may drift out of place within the patient's body. Using the tube when its outlet is not in its proper place may cause serious damage. For example, the tip of a feeding tube may curl up and drift to the patient's lungs. Inserting a feeding solution through the tube in such a case could cause the death of the patient. Likewise, a chemotherapy infusion tube must be placed in a suitable location with a large stream of blood, such as the superior vena-cava in the heart. Otherwise, the medicine may damage the lining of the vascular system. It has been found that of patients who receive medicine in their hearts through infusion tubes, a significant portion suffer from complications due to unnoticed drift of the infusion tube.
There are other cases in which it is desired to follow up on the location of objects, other than tubes, within a patient's body. For example, it may be desired to follow up on the location of a screw, staple, electrode, shunt or any other object implanted in a patient's body. A specific example involves a Murphy button, which is used to connect a torn part of the intestine. The Murphy button is implanted in the intestine, and should remain in place until the intestine heals. After the intestine heals, the Murphy button should drift along the intestine out of the patient's body. Medical staff usually follow up on the movements of the button in case it gets stuck within the patient.
Various methods of confirming the location of medical tubes have been shown in the art. X-ray imaging is the most commonly used location confirmation system. Position determining systems can also be used for this purpose.
U.S. Pat. No. 5,425,382, whose disclosure is incorporated herein by reference, describes apparatus and method for locating a medical tube. The tube is located using a detection apparatus which senses the static magnetic field strength gradient of a magnet associated with the tube. The user locates the tube according to the gradient magnitude at points along the patient's body.
Another method is disclosed in U.S. Pat. Nos. 5,099,845 and 5,325,873, whose disclosures are incorporated herein by reference, wherein a radiating resonant element is associated with the tube. Apparatus is provided to indicate the distance from the apparatus to the tube, according to the radiation levels at different points, whereby the position of the tube is determined.
Another type of position-sensing apparatus is described in U.S. Pat. Nos. 4,905,698 and 5,425,367, whose disclosures are incorporated herein by reference. Such apparatus generates AC currents which induce an electromagnetic field, which in turn induces currents within a coil at the tip of a catheter. According to these currents, the relative location of the catheter is determined.
The use of the above described apparatus is time consuming and therefore complicates the use of intrabody tubes. Also, to operate such apparatus, a certain level of skill and experience is required. Therefore, such apparatus needs to be operated by clinical staff, and is not fit for widespread home care use.